Patient fall monitoring in bathroom in a healthcare facility

ABSTRACT

A patient fall detection system includes a computer and multiple transceivers mounted at fixed locations in a healthcare facility. The transceivers are electronically coupled to the computer. A patient identification tag is worn by a patient and includes a tag transceiver. The high-accuracy locating system monitors a location of the patient ID tag via signals from the tag transceiver to determine whether a patient has entered a bathroom. The computer monitors at least one of an elevation of the patient ID tag in the bathroom, an elevation drop of the patient ID tag in the bathroom, or a time that the patient ID tag has been in the bathroom to determine whether the patient has fallen.

The present application claims the benefit, under 35 U.S.C. § 119(e), ofU.S. Provisional Application No. 62/621,954, filed Jan. 25, 2018, whichis hereby incorporated by reference herein in its entirety.

BACKGROUND

The present disclosure relates to locating systems used in healthcarefacilities to track the locations of patients, and more particularly tobathroom monitoring in a healthcare facility.

Patient rooms in health care facilities are generally equipped with aprivate bathroom for the patient. Patients who are mobile and able toexit their bed may use the bathroom at any time. This may include usingthe bathroom unassisted. However, some patients may inadvertently fallwhile in the bathroom. If a patient falls in the bathroom, significanttime may pass before a caregiver finds the fallen patient because thebathroom door is typically closed preventing the patient from being seenon the bathroom floor. If a caregiver enters the patient room with thebathroom door closed, the caregiver will not know that the patient fellin the bathroom and, therefore, will not have any idea how long it mayhave been since the patient fell. The caregiver may decide to leave thepatient room and plan to return after a period of time under theassumption the patient will exit the bathroom while the caregiver isaway from the patient room.

Some asset tracking tags or badges may include motion sensors such asaccelerometers to monitor patient movement. See, for example, U.S. Pat.No. 7,450,024 in this regard. However, including one or moreaccelerometers in a tracking tag adds to the overall cost and complexityof the tag. Furthermore, if the tag is included as part of a wrist bandon a patient, then abrupt movements of the patient's arm may result in afalse positive signal being sent indicating the patient has fallen when,in fact, the patient has not fallen but has merely moved their armdownwardly with a quick motion, for example.

Additionally, the patient's use of the bathroom may go unnoticed byhousekeeping. That is, if the patient is unattended, housekeeping cannottrack how often the patient is using the bathroom. Because sanitation isparticularly desirable in a healthcare facility, it would be beneficialfor housekeeping to know when the patient's bathroom should be cleaned.Accordingly, there is room for improving the systems and methods ofmonitoring patient use of bathrooms in a healthcare facility.

SUMMARY

The present disclosure includes one or more of the features recited inthe appended claims and/or the following features which, alone or in anycombination, may comprise patentable subject matter.

According to the present disclosure, a patient fall detection system mayinclude a computer that may be configured to track a location of apatient in a healthcare facility. The system may further have aplurality of transceivers that may be mounted at fixed locationsthroughout the healthcare facility and that may be communicativelycoupled to the computer. The system also may have a patientidentification (ID) tag that may be worn by the patient. The patient IDtag may have a tag transceiver that may be configured to communicatewith the plurality of transceivers. The plurality of transceivers andthe computer may cooperate to form a high-accuracy locating system thatmay be operable to determine a location of the patient ID tag in3-dimensional space without the use of any accelerometer. Thehigh-accuracy locating system may determine the location of the patientID tag in the healthcare facility within one foot or less of the patientID tag's actual location. The computer of the high-accuracy locationsystem may be configured to determine whether a patient has entered abathroom of the healthcare facility. If the patient has entered thebathroom, the computer of the high-accuracy locating system maydetermine whether the patient has fallen based on at least one of thefollowing: an elevation of the patient ID tag relative to a referenceplane violating height threshold or an elevation drop of the patient IDtag over a time period exceeding a drop threshold.

In some embodiments, the height threshold may be defined by a height ofa seat of a toilet in the bathroom. The reference plane may be definedas a substantially horizontal plane that passes through at least twotransceivers mounted at a substantially equivalent distance above afloor of the bathroom. Alternatively or additionally, the referenceplane may be defined as a substantially horizontal plane that passesthrough at least two transceivers mounted at a substantially equivalentdistance below a floor of the bathroom. Optionally, if the computerdetermines that the patient has fallen, the computer may initiate analert to a nurse's station or to a wireless communication device of acaregiver.

If desired, the computer of the high-accuracy locating system also maymonitor an amount of time that the patient has been in the bathroom. Thecomputer of the high-accuracy locating system may initiate an alert to anurse's station or to a wireless communication device of a caregiver ifthe amount of time that the patient has been in the bathroom exceeds atime threshold even if the height threshold is not violated and even ifthe drop threshold is not exceeded.

In some embodiments, the computer may track a number of times that thepatient uses the bathroom or enters the bathroom. The computer mayinitiate an alert to a nurse's station or to a wireless communicationdevice of a caregiver if the number of times that the patient uses orenters the bathroom exceeds a predetermined threshold within apredetermined period of time. Alternatively or additionally, thecomputer may initiate an alert to housekeeping if the number of timesthat the patient uses or enters the bathroom exceeds a predeterminedthreshold. The predetermined threshold may be at least three times, forexample.

It is contemplated by this disclosure that the computer of thehigh-accuracy location system may not determine whether the elevation ofthe patient ID tag relative to the reference plane violates the heightthreshold and may not determine if the elevation drop of the patient IDtag over the time period exceeds the drop threshold if the patient isoutside of the bathroom. Thus, the computer of the high-accuracylocation system may determine the elevation of the patient ID tagrelative to the reference plane only after the patient is determined tobe in the bathroom. If desired, the computer may initiate an alert to anurse's station or to a wireless communication device of a caregiverafter the computer determines that the patient ID tag has violated theheight threshold for a predetermined period of time.

In some embodiments, the plurality of transceivers and the tagtransceiver may communicate via ultra-wideband (UWB) signals.Alternatively or additionally, location of the patient ID tag may bedetermined by the computer using two way ranging and time difference ofarrival (TDOA) techniques. Further alternatively or additionally, thecomputer may use signals from only a subset of the plurality oftransceivers to determine the location of the patient ID tag. The subsetmay be determined based on signal strength of signals from the tagtransceiver to the plurality of transceivers. For example, the subsetmay include at least three transceivers from the plurality oftransceivers having highest signal strength values as compared to othersof the plurality of transceivers.

According to another aspect of the present disclosure, a bathroommonitoring system may include a computer, a plurality of transceiversthat may be mounted at fixed locations throughout the healthcarefacility and that may be communicatively coupled to the computer. Thesystem further may include a patient identification (ID) tag that may beworn by a patient. The patient ID tag may have a first tag transceiverthat may be configured to communicate with the plurality oftransceivers. The system also may have a housekeeper identification (ID)tag that may be worn by a housekeeper. The housekeeper ID tag may have asecond tag transceiver that may be configured to communicate with theplurality of transceivers. The plurality of transceivers and thecomputer may cooperate to form a high-accuracy locating system that maybe operable to determine a location of the patient ID tag and thehousekeeper ID tag within one foot or less of the patient ID tag's andhousekeeper ID tag's actual location, respectively. The high-accuracylocating system may monitor a location of the patient via signals fromthe first tag transceiver to determine whether a patient has entered abathroom. The computer may increment a counter to count a number oftimes that the patient enters the bathroom and may initiate an alert tothe housekeeper if the number of times that the patient enters thebathroom exceeds a predetermined threshold. The high-accuracy locationsystem may monitor a location of the housekeeper via signals from thesecond tag transceiver. The computer may reset the counter to zero inresponse to the housekeeper entering the bathroom.

In some embodiments, the predetermined threshold may be three times.Optionally, the computer may track an amount of time that the patienthas been in the bathroom, may compare the amount of time to apredetermined time, and may initiates an alert to a caregiver if theamount of time exceeds the predetermined time. Further optionally, thecomputer of the high-accuracy locating system may determine that thepatient has fallen based on an elevation of the patient ID tag relativeto a reference plane violating a height threshold. The height thresholdmay be defined by a height of a seat of a toilet in the bathroom, forexample.

It is contemplated by this disclosure that the reference plane may bedefined as a substantially horizontal plane that passes through at leasttwo transceivers mounted at a substantially equivalent distance above afloor of the bathroom. Alternatively or additionally, the referenceplane may be defined as a substantially horizontal plane that passesthrough at least two transceivers mounted at a substantially equivalentdistance below a floor of the bathroom. If the computer determines thatthe patient has fallen, the computer may initiate an alert to a nurse'sstation or to a wireless communication device of a caregiver.

In some embodiments, the computer of the high-accuracy locating systemmay determine that the patient has fallen based on an elevation of thepatient ID tag relative to a reference plane violating a heightthreshold for a predetermined amount of time. Alternatively oradditionally, the computer may track a rate of change in an elevation ofthe patient ID tag to determine whether the patient has fallen. Thecomputer may initiate an alert to a nurse's station or to a wirelesscommunication device of a caregiver if the computer determines that thepatient has fallen. If desired, the computer may initiate an alert to anurse's station or to a wireless communication device of a caregiver ifthe number of times that the patient uses or enters the bathroom exceedsa predetermined threshold within a predetermined period of time.

It is within the scope of this disclosure that the bathroom monitoringsystem may further include a caregiver identification tag that mayinclude a caregiver transceiver to communicate with the high-accuracylocating system. The computer may also increment the counter in responseto the caregiver entering the bathroom.

In some embodiments, the first and second tag transceivers maycommunicate with the plurality of transceivers via ultra-wideband (UWB)signals. Alternatively or additionally, the locations of the patient IDtag and the housekeeper ID tag may be determined by the computer usingtwo way ranging and time difference of arrival (TDOA) techniques.Further alternatively or additionally, the computer may use signals fromonly a subset of the plurality of transceivers to determine thelocations of the patient ID tag and the housekeeper ID tag. The subsetmay be determined based on signal strength of signals from the first tagtransceiver and the second tag transceiver to the plurality oftransceivers. For example, the subset may include at least threetransceivers from the plurality of transceivers having highest signalstrength values as compared to others of the plurality of transceivers.

Additional features, which alone or in combination with any otherfeature(s), such as those listed above and/or those listed in theclaims, may comprise patentable subject matter and will become apparentto those skilled in the art upon consideration of the following detaileddescription of various embodiments exemplifying the best mode ofcarrying out the embodiments as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1 is a diagrammatic top plan view of patient rooms of a healthcarefacility showing a high-accuracy locating system operating to track thelocations of patients having patient identification (ID) tags andcaregivers having caregiver ID tags in the patient rooms and bathroomsof the patient rooms;

FIG. 2 is a diagrammatic elevation view of two patient rooms andbathrooms on two different floors showing a patient that has fallen tothe floor in one of the bathrooms and showing reference planes (inphantom) extending through transceivers of the high-accuracy locatingsystem on each of the two floors and showing a height threshold (inphantom) extending through a toilet in the bathroom in which the patienthas fallen;

FIG. 3 is a block diagram showing a first flow chart that isrepresentative of an algorithm to determine if a patient ID tag violatesan elevation criteria which is indicative that a corresponding patienthas fallen in one of the bathrooms;

FIG. 4 is a block diagram showing a second flow chart that isrepresentative of an algorithm to determine if a patient ID tag violatesan elevation drop criteria which is indicative that a correspondingpatient has fallen in one of the bathrooms;

FIG. 5 is a block diagram showing a third flow chart that isrepresentative of an algorithm to determine if a patient ID tag violatesa time threshold which is indicative that a patient in one of thebathrooms may need assistance; and

FIG. 6 is a block diagram showing a fourth flow chart that isrepresentative of an algorithm to determine if patients have entered orused one of the bathrooms a threshold number of times to require ahousekeeper to clean the bathroom.

DETAILED DESCRIPTION

A system 10 to track the whereabouts of caregivers and patients in ahealth care facility such as a hospital or nursing home includes mobilestaff tags 12 worn by staff members such as caregivers and housekeepers,and mobile patient tags 14 worn by patients as shown in FIG. 1. System10 also has a multitude of transceivers, illustratively indicated astransceivers 16 a-16 j in FIG. 1. Transceivers 16 a-16 j are showndispersed throughout four patient rooms 18 a-18 d located on the samefloor of the healthcare facility. Each patient room 18 a-18 d has itsown bathroom 20 a-20 d in the illustrative example. In FIG. 2, a patientroom 18 e with its respective bathroom 20 e is located on the floor ofhealthcare facility below the floor of FIG. 1. In FIG. 2, bathroom 20 eis located directly beneath bathroom 20 a. Additional transceivers 16k-16 m are also shown in FIG. 2. It should be understood that FIGS. 1and 2 are generic representations of a floor plan of a healthcarefacility and so other floor plan configurations of patient rooms andbathrooms are, of course, within the scope of the present disclosure.

Tags 12, 14 and transceivers 16 a-16 m each include a housing thatcontains associated circuitry. The circuitry of tags 12, 14 andtransceivers 16 a-16 m includes for example a processor such as amicroprocessor or microcontroller or the like, memory for storingsoftware, and communications circuitry including a transmitter, areceiver and at least one antenna, for example. Tags 12, 14 also includestructure to enable attachment to caregivers, patients, and otherhospital personnel such as housekeepers. For example, tags 12 mayinclude a necklace so that a caregiver can wear the tag 12 around theirneck or may include a clip so that the caregiver can attach the tag 12to their clothing. Each of tags 14 may include a wristband so that thetags 14 can be worn on the wrists of the associated patients.Transceivers 16 a-16 m each include mounting hardware, such as bracketsor plates or the like, in some embodiments, to permit the transceivers16 a-16 m to be mounted at fixed locations in the rooms 18 a-18 e, 20a-20 e of the healthcare facility with fasteners such as screws or thelike.

Each of rooms 18 a-18 e has a patient bed 22 located therein to supporta respective patient during their stay in the healthcare facility asshown in FIGS. 1 and 2. In the illustrative example, each bathroom 20a-20 e has a toilet 24 and a sink 26. In other embodiments, one or moreof bathrooms 20 a-20 e includes a shower. System 10 further includes ahub computer 30 which is communicatively coupled to other hub computers32 of system 10 via a network 34 of the healthcare facility. In theillustrative example, system 10 is also communicatively coupled to otherremote computers 36 of the healthcare facility. Such other remotecomputers 36 include, for example, nurse call computers, electronicmedical records (EMR) computers, admission/discharge/transfer (ADT)computers, a locating server for handling data from hubs 30, 32, and thelike.

As shown in FIG. 1, system 10 further includes electrical lines 38 thatelectrically couple each of transceivers 16 a-16 j to hub computer 30.For ease of illustration, the electrical lines 38 are depicted as beingrouted through the walls of the various rooms 18 a-18 d. However, itshould be understood that such lines 38 may be routed over a ceilingand/or under a floor of the respective room 18 a-18 d at the discretionof the system designer for any given healthcare facility. Transceivers16 a-16 m communicate wirelessly with tags 12, 14 using radio frequency(RF). It is known that RF signals are able to pass through walls,ceilings, floors, and other objects. Thus, according to this disclosure,it is not required that each room 18 a-18 e and/or bathroom 20 a-20 ehas a transceiver located therein. In fact, each of bathrooms 20 b, 20 ddo not have any transceiver located therein in the illustrative example.

According to this disclosure, system 10 operates as a high-accuracylocating system which is able to determine the location of each tag 12,14 that is in communication with at least three of transceivers 16 a-16m within one foot (30.48 cm) or less of the tag's actual location.System 10 is operable to determine the location of tags 12, 14 in3-dimensional space. Accordingly, FIG. 1 shows X and Y directions andFIG. 2 shows a Z direction which corresponds to the height direction inthe healthcare facility. One example of a high-accuracy locating systemcontemplated by this disclosure is an ultra-wideband (UWB) locatingsystem. UWB locating systems operate within the 3.1 gigahertz (GHz) to10.6 GHz frequency range. Suitable transceivers 16 a-16 m in this regardinclude WISER Mesh Antenna Nodes and suitable tags 12, 14 in this regardinclude Mini tracker tags, all of which are available from WiserSystems, Inc. of Raleigh, N.C. and marketed as the WISER LOCATOR™system.

In some embodiments, system 10 uses 2-way ranging, clocksynchronization, and time difference of arrival (TDoA) techniques todetermine the locations of tags 12, 14 in the X, Y, and Z dimensions.See, for example, International Publication No. WO 2017/083353 A1, whichis hereby incorporated by reference herein in its entirety for all thatit teaches to the extent not inconsistent with the present disclosurewhich shall control as to any inconsistencies, for a detailed discussionof the use of these techniques in a UWB locating system. Using thesetechniques, distances between the stationary transceivers 16 a-16 m andthe various mobile tags 12, 14 are determined based on bidirectionalwireless signals communicated between tags 12, 14 and transceivers 16a-16 m. For example, the distance from each transceiver 16 a-16 m to anyparticular tag can be resolved onto the X-Y plane as a circle having aradius equal to the distance and having its center at the particulartransceiver 16 a-16 m. The actual location of the mobile tag 12, 14 isdetermined based on the point of intersection of three or more of thecircles defined by radii from three or more corresponding transceivers16 a-16 m.

It should be appreciated that, unless a tag 12, 14 is midway between twotransceivers 16 a-16 m on a straight line connecting the twotransceivers 16 a-16 m (in which case the two circles generated will betangent to each other at a single point), then two circles that aregenerated from the two transceivers 16 a-16 m will intersect at twopoints such that a circle generated from a third transceiver is neededto determine which of the two points is the one corresponding to thelocation of the tag 12, 14. Generating fourth, fifth, sixth, etc.circles having other transceivers 16 a-16 m as their respective centerswill further increase the accuracy of determining the actual location ofthe particular tag 12, 14. Due to small errors introduced by refractionof the RF signal through solid objects, including walls, people,equipment, etc., the three or more circles in many instances will notintersect at exactly the same point and so interpolation betweenclusters of circle intersections is performed to arrive at thecalculated location of the particular mobile tag 12, 14 of interest onthe X-Y plane. These considerations are discussed in InternationalPublication No. WO 2017/083353 A1 which is already incorporated byreference herein.

Tracking the locations of multiple mobile tags 12, 14 in substantiallyreal time using 2-way ranging, clock synchronization, TDoA, resolutionof circles onto the X-Y plane, and interpolating intersection pointclusters of the circles requires a large amount of computational powerby hub computers 30, 32 and/or the associated locating server 36. Thus,each hub computer 30, 32 receives incoming data from a predeterminednumber of transceivers 16 a-16 m. In the illustrative example of FIG. 1,hub computer 30 receives data from ten transceivers 16 a-16 j. TDCAcquisition Holdings, Inc. of Huntsville, Ala. which does business asTime Domain, makes a hub computer (referred to as the PLUSSynchronization Distribution Panel) that is capable of receivingincoming data from up to 144 transceiver. The locating server orcomputer 36, in turn, receives data from the various hubs 30, 32 andtracks or monitors the locations of tags 12, 14 in the healthcarefacility.

According to this disclosure, when patients wearing tags 14 enter intorespective bathrooms 20 a-20 e while unattended, system 10, or moreparticularly the respective hub computer 30, 32 and/or the associatedlocating server 36 of system 10, enters into a falls monitoring mode ofoperation to monitor the height of tag 14 in the Z-dimension. That is,when a patient uses one of bathrooms 20 a-20 e without any caregiver tag12 also being detected in the same bathroom 20 a-20 e with the patient,system 10 enters into the falls monitoring mode. In some embodiments,system 10 includes a door monitor or sensor 40 for each bathroom 20 a-20e. Sensors 40 each provide a signal indicative or whether the associateddoor 42 is closed. In such embodiments, system 10 enters the fallsmonitoring mode if any patient is in the respective bathroom 20 a-20 ewithout a caregiver and with the corresponding door 42 being closed assensed by the associated sensor 40. If the bathroom door is open,caregivers are able to see whether the patient has fallen if a caregiveris present in the adjacent room 18 a-18 e, for example.

To determine that the patient is in one of bathrooms 20 a-20 e based onsignals from the respective tag 14 of the patient, one or more ofcomputers 30, 32, 36 compares the X and Y coordinates of the respectivepatient tag 14 with X and Y coordinate ranges that correspond to thevarious bathrooms 20 a-20 e. Thus, an arbitrary origin of the X-Ycoordinate system is established on the floor plan of the healthcarefacility for each floor. Using bathroom 20 a as an example, an origin 50is established at the lower left corner of room 18 a as shown in FIG. 1.Assuming that room 18 a is a 20 foot by 20 foot room with bathroom 20 aoccupying a 10 foot by 10 foot space of the room 18 a, then tag 14 andthe associated patient is considered to be in the bathroom if the Xcoordinate is between 0 feet and 10 feet and the Y coordinate is between10 feet and 20 feet, or more precisely, if the X coordinate is between 0inches and 120 inches and the Y coordinate is between 120 inches and 240inches. These X, Y coordinates for bathroom 20 a correspond to the upperleft quadrant of room 18 a in the illustrative example. In a similarmanner, the X, Y coordinates corresponding to bathrooms 20 b-20 d arealso established relative to origin 50.

It should be appreciated that the room geometry and floor plan shown inFIG. 1 is a simplified example for purposes of illustrating the generalconcept of how one or more of computers 30, 32, 36 are programmed todetermine whether a tag 14 is in a bathroom 20 a-20 e. The placement oforigin 50 in any given floor plan of any given health care facility isat the discretion of the system programmer and the X, Y coordinateranges corresponding to bathrooms of any given healthcare facility willvary from facility to facility based on room geometry. In someembodiments, one of transceivers 16 a-16 m may be chosen as the originfor the X, Y coordinate system if desired.

After system 10 enters into the falls monitoring mode, one or more ofcomputers 30, 32, 36 of system 10 determines whether a patient hasfallen in the particular bathroom 20 a-20 e based on the position of therespect tag 14 in the Z-dimension as compared to a height thresholdmeasured from a substantially horizontal reference plane. Referring toFIG. 2, a substantially horizontal first reference plane 44 is definedthrough the transceivers 16 a-16 j mounted in the rooms of theillustrative upper floor of the healthcare facility and a substantiallyhorizontal second reference plane 46 is defined through transceivers 16k-16 m mounted in the rooms of the lower floor of the healthcarefacility. In FIG. 2, only transceivers 16 a, 16 b, 16 c are shown inconnection with the upper floor and only transceivers 16 k, 16 l, 16 mare shown in the connection with the lower floor. However, it should beunderstood that planes 44, 46 pass through other transceivers mounted inthe rooms of the respective upper and lower floors. To establishsubstantially horizontal planes 44, 46, the associated transceiversshould be mounted at substantially the same elevations, such as may bemeasured downwardly from a ceiling of the upper or lower floor orupwardly from the floor of the upper or lower floor.

In the illustrative example of FIG. 2, a threshold plane 48 is alsoestablished and is shown to be about the height of a seat of toilet 24.Plane 48 may be established at other heights in other embodiments at thediscretion of the system designer. Thus, plane 48 may be at somearbitrary height so as to be above the toilet seat or below the toiletseat. As a general proposition, when tag 14 of the patient is belowplane 48 it is an indication that the patient has likely fallen and whenthe tag 14 of the patient is above plane 48 it is an indication that thepatient likely has not fallen. To determine whether tag 14 is above orbelow plane 48 in the Z-dimension, calculations can be made from eitherof the reference planes 44, 46.

The reference plane 44, 46 on which to base the calculations can beselected based on signal strength between tag 14 and receivers 16 a-16m, for example. That is, the transceivers on the upper floor are used ifthe signal strengths between some or all of the upper floor transceiversand tag 14 are larger than those between some or all of the lower floortransceivers and tag 14, and vice versa. In some embodiments, the threetransceivers 16 a-16 m having the highest signal strength may be usedregardless of whether they are located on the upper or lower floor.Referring to FIG. 2, a likely scenario is that transceivers 16 a, 16 kand 16 l are the three transceivers having the highest signal strengthwith tag 14 in bathroom 20 a. In that instance, the Z coordinate of tag14 in FIG. 2 is determined using transceivers 16 a, 16 k and 16 l. Insome embodiments, more than three of transceivers 16 a-16 m are used todetermine the Z coordinate of tag 14.

In some embodiments, to determine whether or not tag 14 is below thethreshold plane 48 using reference plane 46, the hub computer 32associated with bathroom 20 e and/or the server 36 compares distance Z1,which is defined as the substantially vertical distance betweenreference plane 46 and tag 14, with distance Z3 which is a thresholddistance defined substantially vertically between plane 46 and plane 48.If Z1 is less than Z3, then tag 14 is below plane 48 and if Z1 isgreater than Z3, then tag 14 is above plane 48. If Z1 equals Z3, thenthe system designer can decide whether or not that particular condition,as rare as it would likely occur, is considered to be indicative of thepatient having fallen.

In some embodiments, to determine whether or not tag 14 is below thethreshold plane 48 using reference plane 44, the hub computer 30associated with bathroom 20 a and/or the server 36 compares distance Z2,which is defined as the substantially vertical distance betweenreference plane 44 and tag 14, with distance Z4 which is a thresholddistance defined substantially vertically between plane 44 and plane 48.If Z2 is greater than Z4, then tag 14 is below plane 48 and if Z2 isless than Z4, then tag 14 is above plane 48. If Z2 equals Z4, then thesystem designer can decide whether or not that particular condition, asrare as it would likely occur, is considered to be indicative of thepatient having fallen.

In some embodiments, the Z coordinate of tag 14 is determined relativeto the established origin 50 in the Z dimension and then compared to Zcoordinate ranges corresponding to tag 14 being below reference plane 48and above the corresponding floor surface. Thus, in each of the abovedescribed examples, the basic idea is that an elevation of tag 14 iscompared to a threshold in the Z-dimension to determine if the Zdimension threshold is violated in which case it can be concluded thatthe patient wearing tag 14 has likely fallen in the bathroom.

In the illustrative example, tag 14 is included as part of a wrist bandworn by the patient. It is possible that, while the patient is in thebathroom, including while sitting on the toilet, the patient maytemporarily reach down below plane 48 with their hand to pick up an itemfrom the floor or scratch their ankle or for some other reason. Thus, itis contemplated by this disclosure that, in some embodiments, before afalls determination is made with regard to the patient, tag 14 must bedetermined to be below plane 48 for a threshold period of time, such asabout 10 seconds to just to pick an arbitrary number. Time thresholdsabove and below about 10 seconds, such as between about 5 seconds andabout 30 seconds just to give another set of arbitrary examples, arewithin the scope of this disclosure.

Referring now to FIG. 3, a flow chart of an algorithm 60 that isillustrative of the above described steps for monitoring patient fallsin bathrooms 20 a-20 e is provided. Algorithm 60 is embodied as softwareon one or more of computers 30, 32, 36. In one embodiment, for example,all steps of algorithm 60 are performed on a locating server 36 thatreceives location data from each of hubs 30, 32. In other embodiments,some steps of algorithm 60 are performed on hubs 30, 32, some areperformed on the locating server 36, and optionally, some steps areperformed on some other server or computer 36 such as a server 36 of anurse call system or electronic medical records (EMR) server. Algorithm60 is executed in connection with each tag 14 being monitored. Thus, thediscussion below relates to a single tag 14, but is applicable to alltags 14 being monitored in system 10.

Step 62 begins the algorithm 60 by determining the location of a patienttag 14 in the X and Y dimensions. After the X, Y dimension location(e.g., the X and Y coordinates) of the tag 14 is determined at step 62,algorithm 60 proceeds to step 64 to determine whether the tag 14, andtherefore the associated patient, is in one of bathrooms 20 a-20 e. Ifnot, algorithm 60 loops back to step 62 and proceeds from there. If thepatient is determined to be in one of the bathrooms 20 a-20 e, algorithm60 proceeds to step 66 to determine a location of the tag 14 in the Zdimension. This Z dimension determination can be in accordance with anyof the examples given above with regard to reference planes 46, 48 orwith regard to a substantially horizontal plane passing through theorigin 50 or with regard to any other substantially horizontal referenceplane chosen by the system designer (e.g. sea level or a floor of thehealthcare facility).

After the Z dimension of the tag 14 is determined, the algorithm 60proceeds to step 68 and determines whether the tag 14 violates theZ-dimension threshold such as being below plane 48 in the abovedescribed example. If the location of tag 14 in the Z dimension does notviolate the Z-dimension threshold, then algorithm 60 loops back to step62 and proceeds from there. If the location of tag 14 violates theZ-dimension threshold, the algorithm 60 proceeds to step 70 to determinewhether the Z-dimension threshold violation has exceeded a timethreshold. If not, the algorithm 60 loops back to step 62 and proceedsfrom there. If the time threshold at step 70 has been exceeded, thenalgorithm 70 proceeds to step 72 to alert a caregiver that the patientassociated with the violating tag 14 has likely fallen in the bathroom20 a-20 e in which that particular patient is located. In a variant ofalgorithm 60, step 70 is omitted and the alert to a caregiver at step 72is performed immediately after step 68 in response to the tag 14position in the Z dimension being violated. Such a variant algorithm maybe desirable, for example, if tag 14 is worn on a necklace around thepatient's neck or is attached to an upper torso covering portion of agown of the patient.

The present disclosure contemplates several ways in which to alert acaregiver of a patient bathroom fall in accordance with step 72. Forexample, the locating server 36 sends a message to a nurse call server36 in some embodiments and the nurse call server 36 initiates an alertmessage to a mobile device carried by one or more caregivers assigned tothe particular patient. See U.S. Pat. No. 7,319,386, which is herebyincorporated by reference herein in its entirety for all that it teachesto the extent not inconsistent with the present disclosure which shallcontrol as to any inconsistencies, for a discussion of the use of anurse call system to send alert messages to pagers, telephone handsets,communication badges, mobile phones, and the like. Alternatively oradditionally, the locating server 36 initiates an alert message to acaregiver's mobile device without involving any nurse call system server36. Reference number 36 is used in FIG. 1 to represent a multitude ofcomputer devices including computer devices of nurse call systems, EMRsystems, and other types of healthcare information systems such aspharmacy systems, laboratory systems, and the like. In addition to, orin lieu of, displaying visual alerts (e.g., illuminating a light ordisplaying a message) on various devices just described, an audiblealert such as an alert tone or verbal message may be emitted from one ormore of the various devices that alert caregivers in connection withstep 72 of algorithm 60.

In some embodiments, an indicator light, which is sometimes referred toas a dome light, of a nurse call system is illuminated outside thepatient room 18 a-18 e to alert caregivers in the vicinity of the lightof the bathroom fall alert in connection with step 72 of algorithm 60.See U.S. Pat. No. 8,384,526, which is hereby incorporated by referenceherein in its entirety for all that it teaches to the extent notinconsistent with the present disclosure which shall control as to anyinconsistencies, for a discussion of a suitable indicator light of anurse call system. Messages regarding a bathroom falls alert appear onother displays, such as a master nurse station computer 36, a statusboard display 36, one or more graphical room stations 36 of a nurse callsystem, and one or more staff stations 36 of a nurse call system arealso examples of caregiver alerts of step 72 of algorithm 60 in someembodiments. Further details of these devices used in nurse call systemsas well as other types of related equipment included in variousembodiments of nurse call systems (as well as network 34, in general)can be found in U.S. Pat. Nos. 7,538,659; and 5,838,223 and in U.S.Patent Application Publication Nos. 2009/0217080; 2009/0212956; and2009/0212925, each of which is hereby incorporated by reference hereinin its entirety for all that it teaches to the extent not inconsistentwith the present disclosure which shall control as to anyinconsistencies, as well as in U.S. Pat. Nos. 8,384,526 and 7,319,386which are already incorporated herein by reference.

The present disclosure further contemplates an algorithm 80, shown inFIG. 4, in which a rapid drop of tags 14 while in bathrooms 20 a-20 eand while the respective patient is unattended by a caregiver and, insome embodiments, while the corresponding bathroom door 42 is closed assensed by the associated sensor 40. Algorithm 80 is discussed below inconnection with a single tag 14, but is applicable to all tags 14 beingmonitored in system 10 in those embodiments including algorithm 80. Aswas the case with algorithm 60, algorithm 80 is embodied as software onone or more of computers 30, 32, 36.

The first two steps 62, 64 of algorithm 80 are the same as the first twosteps 62, 64 of algorithm 60 described above. Thus, the description ofthese two steps 62, 64 does not need to be repeated. If the patient isdetermined to be in the bathroom at step 64, then algorithm 80 proceedsto step 66′ in with the location of tag 14 in the Z dimension isdetermined at time T1. This Z-dimension determination can be inaccordance with any of the examples given above with regard to referenceplanes 46, 48 or with regard to a substantially horizontal plane passingthrough the origin 50 or with regard to any other substantiallyhorizontal reference plane chosen by the system designer. However,according to step 66′, a time T1 is associated with the particularZ-dimension determination.

After the Z-dimension determination is made at block 66′, algorithm 80proceeds to block 82 and implements a time delay. The time delay isrelatively short, such as on the order of about an ⅛ second to about 1second, in some embodiments. However, other time delays that are lessthan about ⅛ second or more than about 1 second are within the scope ofthe present disclosure at the option of the system designer. After thetime delay of block 82, algorithm proceeds to block 66″ and determinesthe location of tag 14 in the Z-dimension at time T2. Time T2 occurs thetime delay after time T1. After the Z-dimension at time T2 isdetermined, the algorithm 80 proceeds to step 84 and a determination ismade as to whether the elevation drop (e.g., change inZ-dimension/(T2−T1) or dZ/dt) has exceeded a threshold.

If the reference plane being used is below the tag 14, then assuming tag14 has moved downwardly in elevation such that the elevation at time T2is less than the elevation at T1, then dZ/dt should be a negativenumber. However, if the reference plane being used is above the tag,then assuming tag 14 has moved downwardly in elevation such that theZ-dimension measured downwardly from the overlying reference plane attime T2 is more than the Z-dimension measured downwardly from theoverlying reference plane at time T1, then dZ/dt should be a positivenumber. In either case, dZ/dt can be ignored in the event that itindicates upward movement of tag 14 rather than downward movement. Thatis, in the case of a reference plane below tag 14, then a positive dZ/dtindicates upward movement of tag 14 and, in the case of a referenceplane above tag 14, then a negative dZ/dt indicates upward movement oftag 14.

From the foregoing discussion, the statement at step 84 that theelevation drop dZ/dt is being checked to see if it has “exceeded” athreshold means that, if the reference plane is below the tag 14, thenthe elevation drop dZ/dt is considered to have exceeded the threshold ifit is more negative than the threshold which is a negative number and,if the reference plane is below the tag 14, then the elevation dropdZ/dt is considered to have exceeded the threshold if it is morepositive than the threshold which is a positive number. In either case,the system designer needs to be cognizant of the reference planelocation relative to the tag 14 in connection with programming themathematical rules associated with step 84 of algorithm 80.

If at step 84 the elevation drop, dZ/dt, has not exceeded the threshold,then algorithm loops back to step 62 and proceeds from there. If at step84 the elevation drop, dZ/dt, has exceeded the threshold, then algorithm80 proceeds to step 72 to alert a caregiver that the patient in thebathroom has likely fallen. The various types of caregiver alertsdiscussed above in connection with step 72 of algorithm 60 are equallyapplicable to step 72 of algorithm 80. Algorithm 80 permits theelevation drop, dZ/dt, of each tag 14 to be determined without the useof an accelerometer in the tags 14. By avoiding the use of anaccelerometer in tags 14, the circuitry of tags 14 does not need to beas complex and expensive as the prior art tags 14 that include anaccelerometer.

The present disclosure further contemplates an algorithm 90, shown inFIG. 5, in which a total time of tags 14 being in respective bathrooms20 a-20 e is monitored and, in some embodiments, while the respectivepatient is unattended by a caregiver and/or while the correspondingbathroom door 42 is closed as sensed by the associated sensor 40.Algorithm 90 is discussed below in connection with a single tag 14, butis applicable to all tags 14 being monitored in system 10 in thoseembodiments including algorithm 90. As was the case with algorithm 60,algorithm 90 is embodied as software on one or more of computers 30, 32,36.

The first two steps 62, 64 of algorithm 90 are the same as the first twosteps 62, 64 of algorithm 60 described above. Thus, the description ofthese two steps 62, 64 does not need to be repeated. If the patient isdetermined to be in the bathroom at step 64, then algorithm 90 proceedsto step 92 to start a timer which keeps track of the total or overallamount of time that tag 14, and therefore, the patient wearing tag 14,has been in the bathroom 20 a-20 e since first entering it. At step 94,the timer is monitored and a determination is made as to whether thepatient's time in the bathroom has exceeded a time threshold. The timethreshold may be on the order of about 20 minutes to about 30 minutesjust to give a couple of arbitrary examples. A time threshold lower than20 minutes or greater than 30 minutes is within the scope of thisdisclosure.

If the patient's time in the bathroom has not exceeded the timethreshold, then algorithm 90 loops back to step 62 and proceeds fromthere. If the patient's time in the bathroom has exceeded the timethreshold at step 94, then algorithm proceeds to step 72 to alert acaregiver that the patient has been in the bathroom for an amount oftime that exceeds the time threshold. The various types of caregiveralerts discussed above in connection with step 72 of algorithm 60 areequally applicable to step 72 of algorithm 90. Algorithm 90, therefore,results in an alert to one or more caregivers if a patient has been inone of bathrooms 20 a-20 e for an extended period of time and may needassistance even though there is no indication that the patient may havefallen in the bathroom.

According to the present disclosure and with reference to FIG. 6, system10 is also configured, in some embodiments, with an algorithm 100 tonotify housekeeping after a patient has used the bathroom 20 a-20 e oftheir patient room 18 a-18 e a set number of times so that the bathroomcan be cleaned. The first two steps 62, 64 of algorithm 100 are the sameas the first two steps 62, 64 of algorithm 60 described above and sothese do not need to be repeated. If the patient is determined to be inthe respective bathroom 20 a-20 e, algorithm 100 proceeds to step 102 toincrement a bathroom usage counter. The bathroom usage counter ofalgorithm 100 is incremented at step 102 even if a caregiver accompaniesthe patient into the bathroom and even if door 42 remains opened. Thisis because algorithm 100 is monitoring the overall number of times thebathroom 20 a-20 e has been used since the last time the particularbathroom 20 a-20 e has been cleaned. After step 102, algorithm 104determines whether the bathroom usage counter has exceeded a threshold.The bathroom usage threshold is three usages in some embodiments, forexample, but a threshold greater than or less than three is within thescope of this disclosure at the discretion of the system designer.

If at step 104 the counter has not exceeded the threshold, algorithm 100loops back to step 62 and proceeds from there. If at step 104 thecounter has exceeded the threshold, then algorithm 100 proceeds to step72′ to alert housekeeping that the bathroom 20 a-20 e needs to becleaned. Alerting housekeeping at step 72′ includes sending a message toa housekeeping server 36 in some embodiments. The housekeeping server 36may initiate an alert message to a mobile device carried by one or morehousekeepers assigned to the particular patient room 18 a-18 e in someembodiments. Alternatively or additionally, the locating server 36 mayinitiate an alert message to a housekeeper's mobile device withoutinvolving any housekeeping server 36. In some embodiments, the indicatorlight or dome light outside the patient's room 18 a-18 e, is illuminatedto alert caregivers or housekeepers in the vicinity of the light thatthe associated bathroom 20 a-20 e needs to be cleaned. Alert messagesregarding the need for the bathroom 20 a-20 e to be cleaned may appearon other displays, such as a master nurse station computer 36, a statusboard display 36, one or more graphical room stations 36 of a nurse callsystem, and one or more staff stations 36 of a nurse call system in someembodiments. Audible alerts on the above-mentioned devices are alsocontemplated in connection with step 72′ of algorithm 100.

In some embodiments, an alert may also be sent to a caregiver inconnection with step 72′ of algorithm 100 if an assigned patient usesthe bathroom 20 a-20 e a threshold number of times within a given periodof time, such as during the assigned caregiver's shift. Multiple uses ofthe bathroom 20 a-20 e by the patient within a given time frame mayindicate a medical condition that requires the caregiver's attention.Thus, a timer may be employed in a variant of algorithm 100 formonitoring an amount of time that elapses for a threshold number ofbathroom usages by the patient. The timer may be used to establish atime window (e.g., an 8-hour shift or 5-hours or some other time) withinwhich a caregiver is notified if the patient uses the bathroom athreshold number of times (e.g., four times per shift or three timeswithin a 5-hour window just to list a couple arbitrary examples). Thethreshold number of bathroom uses for caregiver notification may be adifferent number than the threshold number of uses for housekeepernotification according to the present disclosure.

System 10 also monitors the whereabouts of housekeepers according to thepresent disclosure by monitoring the location of tags 12 worn by thehousekeepers. Thus, if a housekeeper enters one or more of bathroom 20a-20 e for which a housekeeping alert has been sent in connection withstep 72′ of algorithm 100, then it is assumed that the housekeeper iscleaning the bathroom and the bathroom usage counter associated withstep 102 of algorithm 100 is reset back to zero. It is also possiblethat a housekeeper may clean one or more of bathrooms 20 a-20 e, such ason a regular cleaning schedule, prior to the bathroom usage counterexceeding the threshold. Under that scenario, the bathroom usage counterassociated with step 102 of algorithm is also reset back to zero sincethe bathroom has been cleaned. In some embodiments, an alert tohousekeeping is sent in response to the bathroom usage counter equalingthe threshold rather than exceeding a threshold (e.g., the thresholdcondition is equal to four bathroom uses, rather than checking for thenext bathroom usage exceeding a threshold of three). Step 104 isconsidered to be representative of both of these scenarios. The bathroomusage counter for housekeeping notification is not reset in response toa caregiver entering the bathroom 20 a-20 e under the assumption thatthe caregiver is assisting the patient and is not cleaning the bathroom20 a-20 e. As was the case with algorithms 60, 80, 90 described above,steps of algorithm 100 may be performed on any one or more of computers30, 32, 36.

System 10 may be configured to run only one of algorithms 60, 80, 90,100 but not the others. Alternatively, system 10 may be configured torun two of algorithms 60, 80, 90, 100 but not the other two. Furtheralternatively, system 10 may be configured to run three of algorithms60, 80, 90, 100 but not the other one. Still further alternatively,system 10 may be configured to run all four of algorithms 60, 80, 90,100. The algorithms 60, 80, 90, 100 may be run in parallel or may be runserially, one after the other, and then the serial sequence is repeated.In each of algorithms 60, 80, 90, 100 the steps subsequent to step 64are not run unless one of tags 14 is first determined to be in one ofbathrooms 20 a-20 e at step 64. Thus, the steps after step 64 ofalgorithms 60, 80, 90, 100 are run only for those tags 14 that aredetermined to be in bathrooms 20 a-20 e and, in some embodiments in thecase of algorithms 60, 80, 90, upon the condition that a caregiver isnot in the corresponding bathroom 20 a-20 e with the respective patientand/or upon the condition that the corresponding bathroom door 42 isclosed as sensed by the associated sensor 40. By limiting the conditionsupon which algorithms 60, 80, 90, 100 proceed to the respective stepsafter step 64, computational power of the computers 30, 32, 36 runningsome or all of algorithms 60, 80, 90, 100 is conserved thereby allowingcomputers to operate more efficiently and to complete other programmedtasks more quickly. Thus, limiting the conditions upon which algorithms60, 80, 90, 100 proceed to the respective steps after step 64 minimizesthe chances that computers 30, 32, 36 become overburdened which wouldhave a tendency to slow down the overall operational efficiency ofsystem 10.

If a caregiver alert or notification is sent to one or more caregiversin connection with algorithms 60, 80, 90, 100 or if a housekeeping alertor notification is sent to one or more housekeepers in connection withalgorithm 100, it is contemplated by this disclosure that, in someembodiments, the alert is cleared from system 10 automatically inresponse to the one or more caregivers or housekeepers, as the case maybe, being located in the respective bathroom 20 a-20 e from which thealert originated. In some embodiments, a caregiver or housekeeper isrequired to provide an input at a computer device 36 in order to clearthe alert after the patient has received the necessary attention orafter the bathroom has been cleaned, as the case may be. For example,caregivers and housekeepers may use graphical room stations 36 of anurse call system that are located in rooms 18 a-18 e to clear theassociated alerts in some embodiments. Alternatively or additionally,inputs to clear the alerts in system 10 may be input on the mobiledevices of caregivers and housekeepers after the patient has receivedthe necessary attention or after the bathroom has been cleaned, as thecase may be.

In some embodiments, an administration screen is provided at thelocating server 36, for example, to permit a system administrator to setthe various thresholds and parameters of algorithms 60, 80, 90, 100. Forexample, the Z-dimension threshold and/or time threshold of algorithm60, the time delay and/or drop threshold of algorithm 80, the timethreshold of algorithm 90, and/or the bathroom usage threshold ofalgorithm 100 may be selectable, such as from associated drop downmenus, or may be otherwise settable by the system administrator usingthe administration screen. These thresholds and parameters may thereforehave different values for different rooms and patients, if desired.

Alternatively or additionally, some or all of the thresholds andparameters just mentioned may be established based on informationprovided to the locating server 36 from other computers 36 of system 10.For example, if a particular patient is designated as a falls risk in anEMR server 36, then the locating server 36 may set a default timethreshold in algorithm 60 for the falls risk patient that is less than adefault time threshold for a patient that is not designated as a fallsrisk. In a similar manner, if a patient has a highly contagious medicalcondition, such as being diagnosed with Methicillin-resistantStaphylococcus aureus (MRSA) bacteria, then the bathroom usage thresholdmay be set to a default value by the locating server 36 that is lessthan the default value set for patients that do not have a MRSAdiagnosis.

Although this disclosure refers to specific embodiments, it will beunderstood by those skilled in the art that various changes in form anddetail may be made without departing from the subject matter set forthin the accompanying claims.

The invention claimed is:
 1. A patient fall detection system comprising:a computer configured to track a location of a patient in a healthcarefacility, a plurality of transceivers mounted at fixed locationsthroughout the healthcare facility and communicatively coupled to thecomputer, and a patient identification (ID) tag that is worn by thepatient, the patient ID tag having a tag transceiver configured tocommunicate with the plurality of transceivers, wherein the plurality oftransceivers and the computer cooperate to form a high-accuracy locatingsystem that is operable to determine a location of the patient ID tag in3-dimensional space without using an accelerometer, the high-accuracylocating system determining the location of the patient ID tag in thehealthcare facility within one foot or less of the patient ID tag'sactual location, wherein the computer of the high-accuracy locationsystem is configured to determine whether a patient has entered abathroom of the healthcare facility, and if the patient has entered thebathroom, the computer of the high-accuracy locating system determineswhether the patient has fallen based on at least one of the following:an elevation of the patient ID tag relative to a reference planeviolating a height threshold or an elevation drop of the patient ID tagover a time period exceeding a drop threshold.
 2. The patient falldetection system of claim 1, wherein the height threshold is defined bya height of a seat of a toilet in the bathroom.
 3. The patient falldetection system of claim 1, wherein the reference plane is defined as asubstantially horizontal plane that passes through at least twotransceivers mounted at a substantially equivalent distance above afloor of the bathroom.
 4. The patient fall detection system of claim 1,wherein the reference plane is defined as a substantially horizontalplane that passes through at least two transceivers mounted at asubstantially equivalent distance below a floor of the bathroom.
 5. Thepatient fall detection system of claim 1, wherein, if the computerdetermines that the patient has fallen, the computer initiates an alertto a nurse's station or to a wireless communication device of acaregiver.
 6. The patient fall detection system of claim 1, wherein thecomputer of the high-accuracy locating system also monitors an amount oftime that the patient has been in the bathroom.
 7. The patient falldetection system of claim 6, wherein the computer of the high-accuracylocating system initiates an alert to a nurse's station or to a wirelesscommunication device of a caregiver if the amount of time that thepatient has been in the bathroom exceeds a time threshold even if theheight threshold is not violated and even if the drop threshold is notexceeded.
 8. The patient fall detection system of claim 1, wherein thecomputer tracks a number of times that the patient uses the bathroom orenters the bathroom.
 9. The patient fall detection system of claim 8,wherein the computer initiates an alert to a nurse's station or to awireless communication device of a caregiver if the number of times thatthe patient uses or enters the bathroom exceeds a predeterminedthreshold within a predetermined period of time.
 10. The patient falldetection system of claim 8, wherein the computer initiates an alert tohousekeeping if the number of times that the patient uses or enters thebathroom exceeds a predetermined threshold.
 11. The patient falldetection system of claim 10, wherein the predetermined threshold is atleast three times.
 12. The patient fall detection system of claim 1,wherein the computer of the high-accuracy location system does notdetermine whether the elevation of the patient ID tag relative to thereference plane violates the height threshold and does not determine ifthe elevation drop of the patient ID tag over the time period exceedsthe drop threshold if the patient is outside of the bathroom.
 13. Thepatient fall detection system of claim 12, wherein the computer of thehigh-accuracy location system determines the elevation of the patient IDtag relative to the reference plane only after the patient is determinedto be in the bathroom.
 14. The patient fall detection system of claim 1,wherein the computer initiates an alert to a nurse's station or to awireless communication device of a caregiver after the computerdetermines that the patient ID tag has violated the height threshold fora predetermined period of time.
 15. The patient fall detection system ofclaim 1, wherein the plurality of transceivers and the tag transceivercommunicate via ultra-wideband (UWB) signals.
 16. The patient falldetection system of claim 1, wherein the location of the patient ID tagis determined by the computer using two way ranging and time differenceof arrival (TDOA) techniques.
 17. The patient fall detection system ofclaim 1, wherein the computer uses signals from only a subset of theplurality of transceivers to determine the location of the patient IDtag, the subset being determined based on signal strength of signalsfrom the tag transceiver to the plurality of transceivers.
 18. Thepatient fall detection system of claim 17, wherein the subset comprisesat least three transceivers from the plurality of transceivers havinghighest signal strength values as compared to others of the plurality oftransceivers.